[Daily News] Global Warming Blues

dava

By Phil Berardelli
ScienceNOW Daily News
6 December 2006

The web of life in Earth's oceans may rest on a more delicate balance than anyone had imagined. Researchers have discovered that even small rises in water temperatures are stifling photosynthesis by tiny marine organisms. If the warming continues, it could mean major changes for animals that feed on plankton and for global climate itself.
Phytoplankton, the microscopic plants that permeate the oceans, underlie the entire marine food chain. And they remove up to 50 billion tons of carbon dioxide per year from Earth's atmosphere--as much as all plant life on the planet's surface. That makes plankton a linchpin in keeping atmospheric CO2 under control.

Ocean plant ecologist Michael Behrenfeld of Oregon State University in Corvallis and colleagues employed a simple technique to monitor the response of phytoplankton to changes in water temperature from 1997 to the present. Using data collected by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), an instrument aboard NASA's OrbView-2 satellite that scans the oceans every 2 days, the team inferred phytoplankton health by calibrating ocean color: greener water meant more plankton activity, while bluer meant less. "We can measure from the satellite in one minute as much [plankton data] as from a ship steaming for 10 years," says oceanographer and team member Gene Carl Feldman of NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Reporting in tomorrow's Nature, Behrenfeld says his team has found the plankton's photosynthesis decreases noticeably with even a slight ocean warming, and that the problem grows more severe as temperatures rise. "When the atmosphere above the ocean warms," he explains, "the upper ocean also warms, creating a barrier between the phytoplankton and their nutrients, which exist in the deep cold dense water." The higher the temperature, he says, the lighter the warmer water, creating a stronger barrier between the top layer, where the phytoplankton dwell, and the depths where nutrients such as nitrogen, phosphorus, and iron tend to collect. This stratification makes it harder for ocean currents and atmospheric winds to mix the water layers enough for the phytoplankton to receive those vital nutrients.

Not all of the news is bad, however. Behrenfeld says warming oceans means increased plankton activity in polar waters, and possibly an increase in the diversity of marine ecosystems worldwide, although further research is needed.

It's an "incredibly beautiful" study, says aquatic biologist Oscar Schofield of Rutgers University in New Brunswick, New Jersey. Because the phytoplankton generate half of the oxygen produced on Earth as well as consuming enormous quantities of CO2, he explains, even a small change in the collective health of the organisms "has a huge impact for life as we know it on this planet." SeaWiFS will greatly help scientists to understand one of the biggest impacts of climate change, he says.

perch88

"Because the phytoplankton generate half of the oxygen produced on Earth as well as consuming enormous quantities of CO2". Is it true? unbelivable.

Now I know why plankton is the favorite topic of GRE essay

dava

It is true, I learned this from somewhere several years ago.

perch88

Kudos, buddy

dava

Thanks, perch88